Power electronic components and devices such as power semiconductors and frequency converters or computer components such as processors and the like are frequently cooled by cooling bodies in the form of cooling plates in which a coolant line is provided, for example shaped in meandering form, to be able to conduct a coolant, for example in the form of a liquid such as water, liquid nitrogen or the like, through the cooling plate. The power electronic components are in contact with the cooling plate to be able to discharge their heat into the cooling plate from where it is then transported away through the cooling medium flowing through. The components to be cooled can in this respect be installed directly on the cooling plate or can be connected to the cooling plate while interposing one or more intermediate layers such as an intermediate layer improving the heat conduction and/or the heat transfer, for example in the form of a conductive paste, such that the aforesaid contact can be direct or indirect.
Such cooling apparatus for power electronic components are known, for example, from document DE 20 2006 012 950 U1 or DE 20 2012 001 323 U1, wherein the latter shows a cooling plate having an intake and a drain which are in flow communication with coolant line sections and pockets formed in the interior of the plate. Document DE 10 2006 040 187 B4 shows a similar cooling apparatus for power electronic components, wherein here a plurality of cooling modules are combined at common inflow manifolds and outflow collectors.
To be able to exactly control the cooling effect of such cooling plates and thus the heat removal of the relatively temperature-sensitive power electronic components, it is helpful to be able to exactly know and to be able to correspondingly control the flow quantity of the coolant flowing through a cooling plate. Flowmeters can be installed in or at the liquid line for determining the flow quantity through a cooling plate, wherein a plurality of such flow sensors are typically used on a use of a plurality of cooling plates. Such flowmeters, for example in the form of ultrasound sensors, are, however, relatively expensive so that high costs are incurred with more complex cooling apparatus. On the other hand, the cooling plates are in this respect often populated very tightly with the electronic components to be cooled such that at times there is only a little space or no space at all available for connecting the named flow sensors.
It is the underlying object of the present invention to provide an improved cooling apparatus of the initially named kind which avoids disadvantages of the prior art and further develops the latter in an advantageous manner. An improved, precise determination of the flow quantity should in particular be made possible with a simple and less expensive sensor system which saves as much space as possible.
The named object is achieved in accordance with the invention by a cooling apparatus for power electronic components having at least one cooling body in the form of a cooling plate which is in contact with at least one power electronic component to be cooled and having a coolant line which is flowed through by a coolant and which leads through the cooling plate, wherein a flow determination device is provided for determining a flow quantity flowing through the cooling plate, wherein the coolant line in the cooling plate has a cross-sectional tapering and has two measurement ports for connecting a differential pressure gauge for measuring a pressure difference at the two measurement ports, with one of the measurement ports being arranged at or directly downstream of the cross-sectional tapering and with the flow determination device comprising an evaluation device for determining the flow quantity from the pressure difference.
It is proposed no longer to determine the flow quantity by means of a plurality of flowmeters, but rather to determine the pressure difference at two suitable points of the coolant line which leads through the cooling body and to determine the flow quantity from the named pressure difference. In accordance with the invention, the coolant line has a cross-sectional tapering in the cooling plate, wherein at least two measurement ports are provided for connecting a differential pressure gauge for measuring a pressure difference at the two measurement ports of which one is provided at or directly downstream of the named cross-sectional tapering at the cooling plate. The flow determination means in this respect comprise an evaluation device for determining the flow quantity from the measured pressure difference. Since the geometry of the coolant line in general and in particular also in the region between the two measurement ports and also the properties of the coolant used, such as the viscosity, are known, the evaluation device can determine the flow quantity through the cooling plate with high precision from the measured pressure difference at the cross-sectional tapering in the cooling plate. The pressure measurement and the pressure sensor system provided for it is substantially less expensive than flowmeters, wherein the design of the cooling plate per se can also be kept simple by the provision of the two measurement ports.
In a further development of the invention, the liquid line between the two measurement ports can have a cross-sectional tapering in the form of a Venturi element. Such a Venturi element can comprise a nozzle-shaped pipe tapering or line tapering, wherein the lowest pressure is adopted at the narrowest point of the line, i.e. where the cross-section is the narrowest and the flow speed is the highest. The dynamic pressure becomes maximum and the static pressure becomes minimal at the constriction of the Venturi nozzle when the liquid cooling medium flows through the Venturi nozzle. On a use of such a cross-sectional tapering or of a Venturi element, the constriction after the tapering and the wide point before the tapering can advantageously be tapped by means of a respective measurement port in order to determine the pressure difference adopted over the cross-sectional tapering by means of the differential pressure sensor.
The Venturi element can in particular form a constriction which is, for example, cylindrical or at least rotationally symmetrical or shaped in another manner and which is adjoined upstream and downstream by inflow and outflow sections with a continuously varying diameter. The named inflow and outflow sections can advantageously be rotationally symmetrical and can form harmoniously shaped tapering or flaring sections which can constantly or harmoniously continue the diameter and/or the cross-section of the constriction in a gently merging manner. The named inflow and outflow sections can, for example, each have a conical contour and can adjoin the constriction in a step-free manner. The Venturi element can preferably form a harmoniously shaped Venturi nozzle.
In a further development of the invention, one of the measurement ports can be provided at the constriction of the Venturi element, whereas another measurement port can be arranged upstream of the inflow section of the Venturi element, in particular in a still untapered section of the coolant line in the cooling plate directly upstream of the inflow section.
In order to be able to provide a nozzle-shaped cross-sectional change not only on one side, but rather on both sides of the constriction of the Venturi element with a reasonable production effort, the Venturi element can form an insert part which is produced separately from the cooling plate, which can be inserted into the cooling plate and which forms a part of the coolant line through the cooling plate in the state inserted into the cooling plate. The Venturi element can advantageously form an insert part which can be inserted into the cooling plate in the longitudinal direction of the coolant line and which can, for example, be pushed and/or screwed into a cooling plate side from an opening of the coolant line at said cooling plate side. The Venturi element can form an insert sleeve.
On a use of a Venturi nozzle, one pressure sensor can be provided or connected in front of the nozzle and one pressure sensor can be provided or connected in the narrow part of the Venturi passage. Since the flow speed is high there, the wall pressure drops greatly there in accordance with the known Bernouilli equation at the Venturi pipe. An advantage of the Venturi solution in this respect is that the pressure difference at the two pressure sensors is considerably larger than with use just of a baffle plate or of a step-shaped cross-sectional tapering. With the same pressure loss of the total measurement device, the measurement with the Venturi nozzle has a substantially greater measurement signal and thus a better resolution. The Venturi passage is advantageously designed as low turbulence for an exact measurement, in particular by a harmonious, gentle extent of the cross-sectional variations free of sharp corners or steps.
To facilitate a low turbulence design of the Venturi passage, an external production of the Venturi nozzle can take place on a lathe. The passage can in this respect be shaped as continuously “rotationally symmetrical” and both the intake and the drain of the narrow point can be designed with a slope to obtain a laminar flow. This increases the precision of the measurement device significantly. With a pure milling in the cooling body from the upper side, the cross-sections cannot truly be produced as rotationally symmetrical and higher turbulence phenomena are obtained. The use of a step drill would have already brought about a better approach to the objective, but can hardly achieve a rotationally symmetrical flaring behind the narrow passage or can only achieve it with difficulty.
The differential pressure gauge can advantageously not comprise a differential pressure sensor which is very expensive and awkward, but can rather comprise two pressure sensor elements which are connected to the measurement ports and which are connectable to the evaluation device, wherein the evaluation device has pressure differential determination means for determining the named pressure difference Δ P from the signals of the two pressure sensor elements.
In this respect, the pressure sensor elements can be installed and fastened directly at the cooling plate or at a sensor holder rigidly fastened to the cooling plate without the interposition of a piping. An exact measurement can hereby be achieved and additional components with corresponding space requirements can be avoided.
Independently of the provision of the named cross-sectional tapering, it can generally be advantageous to provide the measurement ports directly at the cooling body to allow a compact arrangement and a direct measurement at the cooling body. This is, however, not necessary; a corresponding tapering or the tapping over the measurement ports could also be provided at a coolant line section outside the cooling body.
If a plurality of cooling bodies are each preferably used in the form of cooling plates which are each traversed by a coolant line, the intakes of at least some of the cooling bodies can be connected to a common intake manifold and/or their drains can be connected to a common drain collector for a simple design of the piping or of the laying of the lines and to simplify the further handling of the cooling liquid or of the coolant.
With such a plurality of cooling bodies connected to a common intake manifold, it can be advantageous in a further development of the invention to provide a common measurement port in the region of the named intake manifold, whereby the number of measurement ports to be provided in total can be considerably reduced. Only one measurement port has to be provided at the cooling bodies themselves—although naturally a plurality of measurement ports could generally also be provided there—with such a measurement port being able to be provided at the respective cooling body, advantageously downstream of the previously described cross-sectional tapering. Each of the cooling plates can in this respect preferably have the named cross-sectional tapering, in particular in the form of a Venturi element.
With such an arrangement, the differential pressure gauge can preferably be connected in the form of the two pressure sensors to the common measurement point at the intake manifold, on the one hand, and to the respective measurement point of the respective cooling body, on the other hand, to determine the differential pressure between the intake manifold and the measurement point at the cooling body and to be able then to determine the flow quantity through the respective cooling body therefrom. A respective two measurement ports can advantageously also be provided at the cooling plates themselves and can be associated in the named manner with the respective cross-sectional tapering to obtain an increased measurement precision.
If the named plurality of cooling bodies of the cooling apparatus—or at least a subgroup of this plurality of cooling bodies—are connected or combined both at the intake side at a common intake manifold and at the drain side at a common drain collector, it can be advantageous in a further development of the invention also to provide a measurement port at the drain collector in addition to the previously named measurement port at the intake manifold so that the differential pressure sensor can determine the differential pressure between the intake manifold and the drain collector. While taking account of the respective one additional measurement port at the cooling bodies, the total flow quantity through the plurality of the cooling bodies and/or the part flow through a single cooling body can be determined while taking account of the total pressure difference between the inflow manifold and the outflow collector and the individual pressures at the individual cooling bodies, in particular downstream of the previously named Venturi element or of the previously named cross-sectional tapering. For example, the proportion of this cooling body in the total pressure loss can be determined from an individual pressure value which is measured at the one additional pressure port at a cooling body and the flow quantity through this one cooling body can be determined therefrom.
In order to allow a simple connection of the pressure sensors to the cooling plate or to the measurement ports provided thereat, the named measurement ports can have plug and/or screw connections to be able to link the pressure sensors simply by plugging on or screwing on. The named measurement points are in this respect advantageously configured as releasable so that the respective pressure sensor can be connected and released simply.
The pressure gauge can advantageously be connected without interposition of hoses directly to a respective cooling plate or to a port element rigidly connected thereto.
In an advantageous further development of the invention, the temperature of the coolant and/or the temperature of the cooling body is also taken into account in the determination of the flow quantity in order to be able to take account of temperature-dependent changes of the flow quantity, for example by temperature-dependent viscosity changes of the coolant and/or by changes of the coolant line cross-sections caused by thermal material expansions. In an advantageous further development of the invention, at least one temperature sensor can be provided at or in the cooling body, wherein, in a further development of the invention, each cooling body can have at least one temperature sensor on the use of a plurality of cooling bodies. In this respect, in an advantageous further development of the invention, a temperature measurement probe can be provided at the cooling body and can be connected via a signal line to the previously named evaluation unit device or evaluation unit so that the pressure values, on the one hand, and the temperature values, on the other hand, can run together in the evaluation unit.
The evaluation unit can advantageously be connected to a higher-order control which can, for example, control further components of the cooling apparatus, in particular in dependence on the detected flow quantity. For example, a cooling pump can be controlled in dependence on the determined flow quantity to set the flow quantity to a desired value. Alternatively or additionally, a fan can be switched on or switched off in dependence on the determined flow quantity and/or on the measured temperature. Alternatively or additionally, additional cooling bodies can be switched in via valves or additional cooling circuits can be started by setting a coolant pump into motion, wherein, in dependence on the design of the cooling apparatus, other parameters of the cooling apparatus can also be varied by the named higher-order control.
In an advantageous further development of the invention, the evaluation unit can be connected to the higher-order control via a bus system, for example via a field bus or via another cable connection.
The invention will be explained in more detail in the following with respect to preferred embodiments and to associated FIGS.